Pressure indicating devices for sensing and visually indicating fluid pressures are well known in the mechanical art. Such devices are used in almost every industry, and therefore a wide variety of environs and performance criteria must be evaluated before the proper device is selected for a particular use.
Probably the most frequently used pressure-indicating device is the C-spring bourdon-tube pressure gauge. Gauges of this type consist of a flattened tube of spring bronze or steel bent into a circle. Pressure inside the tube tends to straighten the tube. This motion rotates a pointer through a pinion-and-sector mechanism whereby the pointer indicates the pressure on a dial face. The tube may be bent through several turns to form a spiral or helical element to amplify the motion of the pointer.
The simplicity of the bourdon-tube pressure gauge is of great benefit in keeping manufacturing costs down and providing an adequate gauge sufficient for many applications. The pointer-type indicator promotes easily readable pressure readings and promotes the use of easily readable dual scales on one gauge.
Bourdon-tube gauges, because they use a hollow tube into which the fluid to be measured must enter, can be easily plugged by viscous fluids or fluids containing debris and large particulate matter. Bourdon-tube gauge devices are also disadvantageous because the change in volume of the bourdon-tube due to pressure changes is typically very small and therefore efficient dampening is difficult. Shock and vibration also have a very detrimental effect upon this type of gauge.
For the above reasons, other types or designs of pressure indicating devices have been devised and are widely used in the mechanical art. One such device is the diaphragm guage which may employ a capsule composed of two diaphragms bonded by suitable means to either of the axial ends of a short cylinder. The space between may be filled with some relatively imcompressible fluid or other means such that a pressure causing deflection of one diaphragm will cause a corresponding deflection of the opposite diaphragm.
Pressure gauges using diaphragms typically employ suitable mechanical translating mechanisms to translate the relatively small deflection of the diaphragm into a visually readable form. In the past, this form constituted a movable disc with demarcation and numerals thereon which rotates in response to pressure changes on the diaphragm.
The diaphragm-type gauges overcome many of the disadvantages of the bourdon-tube type gauges, i.e., they can be easily dampened by a restricting screw; they are not easily plugged because the fluid to be measured does not enter the device; they are very resistant to shock and vibration; and they are very accurate.
With the foregoing in mind, it is therefore a primary object of the present invention to provide a novel pressure measuring device that offers the advantages of a diaphragm-type gauge with the easy readability of the bourdon-tube type gauge.
It is also a feature of the present invention to provide a pressure measuring device that is resistant to shock and vibration.
Another feature of the present invention is to provide a mechanism that may easily be dampened without significant loss of accuracy.
Among the several features of the present invention is noted the contemplation of a novel pressure measuring device that is uniquely designed to achieve easily readable, accurate and reliable pressure readings when used in conjunction with a "mud" pump commonly used in oil well operations.
Other and further objects, advantages and features of the present invention will become apparent to one skilled in the art upon consideration of this entire disclosure. The form of the invention, which will now be described in detail, illustrates the general principles of the invention, but it is to be understood that this detailed description is not to be taken as limiting the scope of the present invention.